scholarly journals Epstein-Barr virus latent membrane protein 2A is a B-cell receptor mimic and essential for B-cell survival

Blood ◽  
2007 ◽  
Vol 110 (10) ◽  
pp. 3715-3721 ◽  
Author(s):  
Christoph Mancao ◽  
Wolfgang Hammerschmidt
Keyword(s):  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Cell Receptor ◽  
Latent Membrane Protein ◽  
B Cell Receptor ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Epstein Barr

AbstractMany cells latently infected with Epstein-Barr virus (EBV), including certain virus-associated tumors, express latent membrane protein 2A (LMP2A), suggesting an important role for this protein in viral latency and oncogenesis. LMP2A mimics B-cell receptor signaling but can also act as a decoy receptor blocking B-cell receptor (BCR) activation. Studies of peripheral B cells have not resolved this apparent contradiction because LMP2A seems to be dispensable for EBV-induced transformation of these B cells in vitro. We show here that LMP2A is essential for growth transformation of germinal center B cells, which do not express the genuine BCR because of deleterious somatic hypermutations in their immunoglobulin genes. BCR-positive (BCR+) and BCR-negative (BCR−) B cells are readily transformed with a recombinant EBV encoding a conditional, floxed LMP2A allele, but the survival and continued proliferation of both BCR+ and BCR− B cells is strictly dependent on LMP2A. These findings indicate that LMP2A has potent, distinct antiapoptotic and/or transforming characteristics and point to its role as an indispensable BCR mimic in certain B cells from which human B-cell tumors such as Hodgkin lymphoma originate.

scholarly journals Epstein-Barr Virus (EBV) Latent Membrane Protein 2A Regulates B-Cell Receptor-Induced Apoptosis and EBV Reactivation through Tyrosine Phosphorylation

2005 ◽  
Vol 79 (13) ◽  
pp. 8655-8660 ◽  
Author(s):  
Makoto Fukuda ◽  
Richard Longnecker
Keyword(s):  
Membrane Protein ◽  
Epstein Barr Virus ◽  
Cell Receptor ◽  
Latent Membrane Protein ◽  
B Cell Receptor ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Ebv Reactivation ◽  
Epstein Barr ◽  
Induced Apoptosis

ABSTRACT Epstein-Barr virus (EBV) is a human herpesvirus that establishes a lifelong latent infection of B cells. Within the immune system, apoptosis is a central mechanism in normal lymphocyte homeostasis both during early lymphocyte development and in response to antigenic stimuli. In this study, we found that latent membrane protein 2A (LMP2A) inhibited B-cell receptor (BCR)-induced apoptosis in Burkitt's lymphoma cell lines. Genistein, a specific inhibitor of tyrosine-specific protein kinases, blocked BCR-induced apoptosis and EBV reactivation in the cells. These findings indicate that LMP2A blocks BCR-induced cell apoptosis and EBV reactivation through the inhibition of activation of tyrosine kinases by BCR cross-linking.

scholarly journals Epstein-Barr Virus Latent Membrane Protein 2A Preferentially Signals through the Src Family Kinase Lyn

2008 ◽  
Vol 82 (17) ◽  
pp. 8520-8528 ◽  
Author(s):  
Mark Rovedo ◽  
Richard Longnecker
Keyword(s):  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Sh2 Domain ◽  
Latent Membrane Protein ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT Latent membrane protein 2A (LMP2A) is a viral protein expressed during Epstein-Barr virus (EBV) latency in EBV-infected B cells both in cell culture and in vivo. LMP2A has important roles in modulating B-cell receptor signal transduction and provides survival and developmental signals to B cells in vivo. Although Lyn has been shown to be important in mediating LMP2A signaling, it is still unclear if Lyn is used preferentially or if LMP2A associates promiscuously with other Src family kinase (SFK) members. To investigate the role of various SFKs in LMP2A signaling, we crossed LMP2A transgenic mice (TgE) with Lyn−/−, Fyn−/−, or Blk−/− mice. TgE Lyn−/− mice had a larger immunoglobulin M (IgM)-positive B-cell population than TgE mice, suggesting that the absence of Lyn prevents LMP2A from delivering survival and developmental signals to the B cells. Both TgE Fyn−/− and TgE Blk−/− mice have an IgM-negative population of splenic B cells, similar to the TgE mice. LMP2A was also transiently transfected into the human EBV-negative B-cell line BJAB to determine which SFK members associate with LMP2A. Lyn was detected in LMP2A immunoprecipitates, whereas Fyn was not. Both Lyn and Fyn were able to bind to an LMP2A mutant which contained a sequence shown previously to bind tightly to the SH2 domain of multiple SFK members. From these results, we conclude that LMP2A preferentially associates with and signals through Lyn compared to its association with other SFKs. This preferential association is due in part to the SH2 domain of Lyn associating with LMP2A.

scholarly journals Rewiring of B cell receptor signaling by Epstein–Barr virus LMP2A

2020 ◽  
Vol 117 (42) ◽  
pp. 26318-26327
Author(s):  
Kamonwan Fish ◽  
Federico Comoglio ◽  
Arthur L. Shaffer ◽  
Yanlong Ji ◽  
Kuan-Ting Pan ◽  
...  
Keyword(s):  
Cell Cycle ◽  
B Cells ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Barr Virus ◽  
Human B Cells ◽  
Bcr Signaling ◽  
Epstein Barr

Epstein–Barr virus (EBV) infects human B cells and reprograms them to allow virus replication and persistence. One key viral factor in this process is latent membrane protein 2A (LMP2A), which has been described as a B cell receptor (BCR) mimic promoting malignant transformation. However, how LMP2A signaling contributes to tumorigenesis remains elusive. By comparing LMP2A and BCR signaling in primary human B cells using phosphoproteomics and transcriptome profiling, we identified molecular mechanisms through which LMP2A affects B cell biology. Consistent with the literature, we found that LMP2A mimics a subset of BCR signaling events, including tyrosine phosphorylation of the kinase SYK, the calcium initiation complex consisting of BLNK, BTK, and PLCγ2, and its downstream transcription factor NFAT. However, the majority of LMP2A-induced signaling events markedly differed from those induced by BCR stimulation. These included differential phosphorylation of kinases, phosphatases, adaptor proteins, transcription factors such as nuclear factor κB (NF-κB) and TCF3, as well as widespread changes in the transcriptional output of LMP2A-expressing B cells. LMP2A affected apoptosis and cell-cycle checkpoints by dysregulating the expression of apoptosis regulators such as BCl-xL and the tumor suppressor retinoblastoma-associated protein 1 (RB1). LMP2A cooperated with MYC and mutant cyclin D3, two oncogenic drivers of Burkitt lymphoma, to promote proliferation and survival of primary human B cells by counteracting MYC-induced apoptosis and by inhibiting RB1 function, thereby promoting cell-cycle progression. Our results indicate that LMP2A is not a pure BCR mimic but rather rewires intracellular signaling in EBV-infected B cells that optimizes cell survival and proliferation, setting the stage for oncogenic transformation.

scholarly journals Roles of the ITAM and PY Motifs of Epstein-Barr Virus Latent Membrane Protein 2A in the Inhibition of Epithelial Cell Differentiation and Activation of β-Catenin Signaling

2005 ◽  
Vol 79 (4) ◽  
pp. 2375-2382 ◽  
Author(s):  
Jennifer A. Morrison ◽  
Nancy Raab-Traub
Keyword(s):  
Membrane Protein ◽  
Epstein Barr Virus ◽  
Nuclear Translocation ◽  
Cell Receptor ◽  
Latent Membrane Protein ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Cellular Processes ◽  
Epstein Barr ◽  
Virus Latent Membrane Protein

ABSTRACT Epstein-Barr virus (EBV) latent membrane protein 2A (LMP2A) is important for maintenance of latency in infected B lymphocytes. Through its immunoreceptor tyrosine-based activation motif (ITAM) and PY motifs, LMP2A is able to block B-cell receptor (BCR) signaling, bind BCR-associated kinases, and manipulate the turnover of itself and these kinases via a PY-mediated interaction with the Nedd4 family of ubiquitin ligases. In epithelial cells, LMP2A has been shown to activate the phosphatidylinositol 3′-OH kinase/Akt and β-catenin signaling pathways. In the present study, the biological consequences of LMP2A expression in the normal human foreskin keratinocyte (HFK) cell line were investigated and the importance of the ITAM and PY motifs for LMP2A signaling effects in HFK cells was ascertained. The ITAM was essential for the activation of Akt by LMP2A in HFK cells, while both the ITAM and PY motifs contributed to LMP2A-mediated accumulation and nuclear translocation of the oncoprotein β-catenin. LMP2A inhibited induction of differentiation in an assay conducted with semisolid methylcellulose medium, and the PY motifs were critical for this inhibition. LMP2A is expressed in the EBV-associated epithelial malignancies nasopharyngeal carcinoma and gastric carcinoma, and these data indicate that LMP2A affects cellular processes that likely contribute to carcinogenesis.

scholarly journals Epstein-Barr Virus Latent Membrane Protein 2B (LMP2B) Modulates LMP2A Activity

2006 ◽  
Vol 81 (1) ◽  
pp. 84-94 ◽  
Author(s):  
Mark Rovedo ◽  
Richard Longnecker
Keyword(s):  
Signal Transduction ◽  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Tyrosine Phosphorylation ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Cross Linking ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT Latent membrane protein 2A (LMP2A) and LMP2B are viral proteins expressed during Epstein-Barr virus (EBV) latency in EBV-infected B cells both in cell culture and in vivo. LMP2A has important roles in modulating B-cell receptor (BCR) signal transduction by associating with the cellular tyrosine kinases Lyn and Syk via specific phosphotyrosine motifs found within the LMP2A N-terminal tail domain. LMP2A has been shown to alter normal BCR signal transduction in B cells by reducing levels of Lyn and by blocking tyrosine phosphorylation and calcium mobilization following BCR cross-linking. Although little is currently known about the function of LMP2B in B cells, the similarity in structure between LMP2A and LMP2B suggests that they may localize to the same cellular compartments. To investigate the function of LMP2B, B-cell lines expressing LMP2A, LMP2B, LMP2A/LMP2B, and the relevant vector controls were analyzed. As was previously shown, cells expressing LMP2A had a dramatic block in normal BCR signal transduction as measured by calcium mobilization and tyrosine phosphorylation. There was no effect on BCR signal transduction in cells expressing LMP2B. Interestingly, when LMP2B was expressed in conjunction with LMP2A, there was a restoration of normal BCR signal transduction upon BCR cross-linking. The expression of LMP2B did not alter the cellular localization of LMP2A but did bind to and prevent the phosphorylation of LMP2A. A restoration of Lyn levels, but not a change in LMP2A levels, was also observed in cells coexpressing LMP2B with LMP2A. From these results, we conclude that LMP2B modulates LMP2A activity.

scholarly journals c-Myc Represses Transcription of Epstein-Barr Virus Latent Membrane Protein 1 Early after Primary B Cell Infection

2017 ◽  
Vol 92 (2) ◽  
Author(s):  
Alexander M. Price ◽  
Joshua E. Messinger ◽  
Micah A. Luftig
Keyword(s):  
Transcription Factor ◽  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Cell Infection ◽  
Barr Virus ◽  
Epstein Barr ◽  
Factor C

ABSTRACTRecent evidence has shown that the Epstein-Barr virus (EBV) oncogene LMP1 is not expressed at high levels early after EBV infection of primary B cells, despite its being essential for the long-term outgrowth of immortalized lymphoblastoid cell lines (LCLs). In this study, we found that expression of LMP1 increased 50-fold between 7 days postinfection and the LCL state. Metabolic labeling of nascent transcribed mRNA indicated that this was primarily a transcription-mediated event. EBNA2, the key viral transcription factor regulating LMP1, and CTCF, an important chromatin insulator, were recruited to the LMP1 locus similarly early and late after infection. However, the activating histone H3K9Ac mark was enriched at the LMP1 promoter in LCLs relative to that in infected B cells early after infection. We found that high c-Myc activity in EBV-infected lymphoma cells as well as overexpression of c-Myc in an LCL model system repressed LMP1 transcription. Finally, we found that chemical inhibition of c-Myc both in LCLs and early after primary B cell infection increased LMP1 expression. These data support a model in which high levels of endogenous c-Myc activity induced early after primary B cell infection directly repress LMP1 transcription.IMPORTANCEEBV is a highly successful pathogen that latently infects more than 90% of adults worldwide and is also causally associated with a number of B cell malignancies. During the latent life cycle, EBV expresses a set of viral oncoproteins and noncoding RNAs with the potential to promote cancer. Critical among these is the viral latent membrane protein LMP1. Prior work suggests that LMP1 is essential for EBV to immortalize B cells, but our recent work indicates that LMP1 is not produced at high levels during the first few weeks after infection. Here we show that transcription of the LMP1 gene can be negatively regulated by a host transcription factor, c-Myc. Ultimately, understanding the regulation of EBV oncogenes will allow us to better treat cancers that rely on these viral products for survival.

scholarly journals The Epstein-Barr Virus Protein, Latent Membrane Protein 2A, Co-opts Tyrosine Kinases Used by the T Cell Receptor

2005 ◽  
Vol 280 (40) ◽  
pp. 34133-34142 ◽  
Author(s):  
Robert J. Ingham ◽  
Judith Raaijmakers ◽  
Caesar S. H. Lim ◽  
Geraldine Mbamalu ◽  
Gerald Gish ◽  
...  
Keyword(s):  
Membrane Protein ◽  
T Cell Receptor ◽  
Tyrosine Kinases ◽  
Epstein Barr Virus ◽  
Cell Receptor ◽  
Latent Membrane Protein ◽  
Virus Protein ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Epstein Barr

scholarly journals Epstein-Barr Virus Represses the FoxO1 Transcription Factor through Latent Membrane Protein 1 and Latent Membrane Protein 2A

2006 ◽  
Vol 80 (22) ◽  
pp. 11191-11199 ◽  
Author(s):  
Angharad M. Shore ◽  
Paul C. White ◽  
Rosaline C.-Y. Hui ◽  
Abdelkader Essafi ◽  
Eric W.-F. Lam ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Latent Membrane Protein 1 ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Ebv Infection ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) infection is associated with the development of many B-cell lymphomas, including Burkitt's lymphoma, Hodgkin's lymphoma, and posttransplant lymphoproliferative disease. The virus alters a diverse range of cellular molecules, which leads to B-cell growth and immortalization. This study was initiated to investigate the interplay between EBV and a proapoptotic transcription factor target, FoxO1. In this report, we show that EBV infection of B cells leads to the downregulation of FoxO1 expression by phosphatidylinositol 3-kinase-mediated nuclear export, by inhibition of FoxO1 mRNA expression, and by alteration of posttranslational modifications. This repression directly correlates with the expression of the FoxO1 target gene Bcl-6 and inversely correlates with the FoxO1-regulated gene Cyclin D2. Expression of the EBV genes for latent membrane protein 1 and latent membrane protein 2A decreases FoxO1 expression. Thus, our data elucidate distinct mechanisms for the regulation of the proapoptotic transcription factor FoxO1 by EBV.

scholarly journals B Cell Receptor-Responsive miR-141 Enhances Epstein-Barr Virus Lytic Cycle via FOXO3 Inhibition

mSphere ◽  
2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Yan Chen ◽  
Devin N. Fachko ◽  
Nikita S. Ivanov ◽  
Rebecca L. Skalsky
Keyword(s):  
B Cells ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Cell Receptor ◽  
Lytic Replication ◽  
B Cell Receptor ◽  
Lytic Cycle ◽  
Cross Linking ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT Antigen recognition by the B cell receptor (BCR) is a physiological trigger for reactivation of Epstein-Barr virus (EBV) and can be recapitulated in vitro by cross-linking of surface immunoglobulins. Previously, we identified a subset of EBV microRNAs (miRNAs) that attenuate BCR signal transduction and subsequently dampen lytic reactivation in B cells. The roles of host miRNAs in the EBV lytic cycle are not completely understood. Here, we profiled the small RNAs in reactivated Burkitt lymphoma cells and identified several miRNAs, such as miR-141, that are induced upon BCR cross-linking. Notably, EBV encodes a viral miRNA, miR-BART9, with sequence homology to miR-141. To better understand the functions of these two miRNAs, we examined their molecular targets and experimentally validated multiple candidates commonly regulated by both miRNAs. Targets included B cell transcription factors and known regulators of EBV immediate-early genes, leading us to hypothesize that these miRNAs modulate kinetics of the lytic cascade in B cells. Through functional assays, we identified roles for miR-141 and EBV miR-BART9 and one specific target, FOXO3, in progression of the lytic cycle. Our data support a model whereby EBV exploits BCR-responsive miR-141 and further mimics activity of this miRNA family via a viral miRNA to promote productive lytic replication. IMPORTANCE EBV is a human pathogen associated with several malignancies. A key aspect of lifelong virus persistence is the ability to switch between latent and lytic replication modes. The mechanisms governing latency, reactivation, and progression of the lytic cycle are only partly understood. This study reveals that specific miRNAs can act to support the EBV lytic phase following BCR-mediated reactivation triggers. Furthermore, this study identifies a role for FOXO3, commonly suppressed by both host and viral miRNAs, in modulating progression of the EBV lytic cycle.

scholarly journals Epstein–Barr virus latent membrane protein 2A mimics B-cell receptor-dependent virus reactivation

2005 ◽  
Vol 86 (3) ◽  
pp. 551-559 ◽  
Author(s):  
Eveline Schaadt ◽  
Barbara Baier ◽  
Josef Mautner ◽  
Georg W. Bornkamm ◽  
Barbara Adler
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lytic Cycle ◽  
Virus Reactivation ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Receptor Signalling ◽  
Epstein Barr

Latent membrane protein 2A (LMP2A) of Epstein–Barr virus (EBV) shares protein motifs with the B-cell receptor that play a role in B-cell receptor signalling and has been shown to mimic an activated B-cell receptor by providing a survival signal for mature B cells in transgenic mice. Conversely, LMP2A has been reported not to support but to inhibit B-cell receptor signalling with respect to virus reactivation and to block lytic virus induction after anti-Ig treatment of EBV-infected B cells. To solve this apparent paradox, the role of LMP2A in lytic-cycle induction was re-examined in B cells conditionally immortalized by EBV. It was shown that, in the absence of other stimuli, LMP2A expression alone could lead to induction of the virus lytic cycle. Similarly to B-cell receptor stimulation by anti-Ig treatment, this LMP2A-mediated reactivation was dependent on the mitogen-activated protein kinase pathway and could be inhibited by the viral LMP1. Our data reinforce the notion that LMP2A is a functional homologue of the B-cell receptor, not only with respect to B-cell survival but also with respect to regulation of the lytic cycle.

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